12-hydroxystearic acid (hereinafter “12-HSA”) is reported to have a wide variety of beneficial cosmetic effects on skin. It is a known PPAR-alpha (peroxisome proliferator activated receptors sub-type alpha) activator, skin lightening agent, and a sebum secretion inhibitor. See e.g. Alaluf et al. U.S. Pat. No. 6,423,325, Mayes et al. U.S. Pat. No. 6,713,051, WO2006/056283 (Hindustan Lever), Madison US 2009/0317341, Minami et al. U.S. Pat. No. 6,197,343, Granger et al. US2004/0043044.
As such, cosmetic products containing 12-HSA are highly desirable.
JP 09-048962 describes the use of 12-HSA or its salt as an effective constituent of a solidification inhibitor, to inhibit solidification of a liquid detergent or a liquid cosmetic; all the examples containing a fully neutralized salt of 12-HSA. 12-HSA has traditionally been used as gelling agent e.g. in lipsticks and antiperspirant compositions. See also EP 0129528, U.S. Pat. No. 6,680,285, Abbas et al. U.S. Pat. No. 6,680,285, Tanner et al. U.S. Pat. No. 5,759,524, WO95/31961 (Procter &. Gamble), Kawa et al., US 2004/0044078 (describing the use of 12-HSA to increase viscosity of cosmetic compositions), and JP 2010/138,110.
Unfortunately, 12-HSA is a solid having a melting point of about 72 to 77 degrees Celsius, has no water solubility and limited oil solubility. Salts of 12-HSA are only marginally more water-soluble. Because of the high melting temperature it is difficult to formulate in a personal care composition, often requiring elevated temperatures or solvents. Lowering the 12-HSA melting point or at least have it (partially) available as a non-solid may be desirable as this may e.g. influence the bioavailability or ease of use of 12-HSA or personal care compositions comprising 12-HSA. Another drawback associated with the high melting point of 12-HSA is that it may re-crystallize upon storage after being incorporated in a personal care product in non-solid form like e.g. in a solvent. Such re-crystallization may cause the undesired gellation of such personal care products thereby destroying the texture thereof.
Butyl methoxydibenzoylmethane (“BMDM”) is a well-known UV-A organic sunscreen that is used in personal care composition like sunscreen formulations and other skin leave-on compositions to provide protection against the full spectrum of UV-A rays. It is available under the trade name Parsol 1789®. It is a solid having a melting point of about 83 degrees Celsius. As such it may be difficult to formulate in a personal care composition, often requiring elevated temperatures or solvents. BMDM has a finite oil solubility and this characteristic is used to formulate BMDM in for example a sunscreen. As with 12-HSA, BMDM may re-crystallize upon storage after being incorporated in a personal care product in non-solid form like e.g. in a solvent. Such re-crystallization may cause the undesired gellation of such personal care products thereby destroying the texture thereof.
The present inventors have identified a need for alternative methods to incorporate 12-HSA and/or BMDM in personal care products that at least in part do not have one or more of the aforementioned drawbacks.